Hydrophone members



Filed Feb. 5, 1964 VI 2 w l w u [I lilll m w, I W 5 W M 2 d 2\ 5 4 mm 10 2 m 4 5 3,284,760 HYDROPHONE MEMBERS Guy Mas, Neuilly-sur-Seine,France, assignor to LElectronique Applique, Paris, France Filed Feb. 3,1964, Ser. No. 341,929

Claims priority, application Fi-ance, Feb. 5, 1963,

923,762, Patent 1,355,675

3 Claims. (Cl. 340-10) The present invention concerns improvements in orrelating to hydrophone members specially adapated to be used insubmarine listening microphone arrangements of the so-called anti-echokind, i.e. hydrophone arrangements comprising a plurality of members sodimensioned and relatively supported that they do not present anysubstantial response to the echoes on the bottom and surface of the seaof the noises they are intended to pick off.

In the accompanying set of drawings, FIGURE 1 is a diagrammatical viewshowing an arrangement of six hydrophones;

FIGURE 2 is a sectional view of one hydrophone in accordance with thepresent invention;

FIGURE 3 is a sectional view of a modified form of the hydrophone shownin FIGURE 2.

As an illustrative example of such anti-echo arrangements, FIG. 1 showsa diagrammatic view of one of such devices comprising for instance sixhydrophone members distributed in three pairs of identical members ineach pair, referred as 2, 3 and 4 along an hydrophone cable 1 from whichthey depend and from which they are supported. The distribution is suchthat it substantially follows the so-called Tchebyschefl law so that theradiation diagram of the arrangement does not present any substantialsecondary lobes but only a main lobe symmetrical with respect to themid-plane orthogonal to the arrangement. Hydrophone members 2 aredimensioned for the higher weight and hydrophone members 4, for thelower weight in the arrangement, the weight of hydrophone members 3being intermediate between those of members 2 and 4. Consequently thedirectivity of pick-off radiation diagram will be maximum in the saidplane.

It is an object of the invention to provide a structure of an hydrophonemember wherein the weight can be easily determined by the sole choice ofthe height of the piezoelectric cylindrical part incorporated therein asa converter from sound to electrical signal pick-up.

A further object of the invention is to so provide such structure thatthe response is substantially constant over the whole height of thepiezo-electric cylinder.

A furthre object of the invention is to so provide such a structure thatits mechanical and acoustical arrangement is particularly simple andefficient for the sought purposes.

According to the invention, a piezo-electric hydrophone member foranti-echo submarine listening arrangements is mainly characterized bythe combination of a piezo-electric hollow cylinder the height of whichis adjusted for the response efliciency coeflicient thereof, a pair ofplastic material plates applied on the opposite edges of said cylinder,a stretcher within said cylinder and not in contact with it forsupporting said plates, at least one annular sheath tightly applied overthe external surface of the said cylinder and two axial sleevesextending from said plates in an outward direction and watertightlyseparating the input and output cable portions WhlCh are connected tothe piezo-electric cylinder terminals within the so provided watertightinner volume of said cylinder.

With reference to the accompanying drawings, two

' United States Patent,

3,284,760 Patented Nov. 8, 1966 illustrative embodiments of such amember are respectively shown in FIGS. 2 and 3 in cross-section views.In these figures the piezo-electric cylinder 10 is of a height providedfor defining the weight of the member, that 1s to say, as inferredabove, the amount of the response efiiciency coefficient of the memberto any pick-oh noise. The inner stretcher 16 is in two parts or at leastis provided with a hollowed intermediary portion as shown at 20 forsplicing the cable 1 and making therefrom electrical connections such as17 to the electrode terminals 21 and 22 on the outer and inner faces ofthe cylinder 10 through leads 18 and 19. The electrode terminals may bemade by metallizing of said faces and the leads 18 and 19 may besoldered to said terminals at one end thereof and at wires of the cable'1 at the other end thereof. The stretcher 16 has preferably the shapeof a spool with two end flanges each of a smaller diameter than theinner diameter of the cylinder 10. When the spool is provided in twoparts, it may be used for aflixing the cable passing through the memberso as to avoid undue traction stretch thereon.

With special reference to FIG. 2 over the flanges of the spool 16 areapplied two circular plates 13 and 23 of a plastic material such asrubber or the like, extension sleeves 15 and 25 of which constitutesheaths for the incoming and outcoming portions of the cable 1. Thewatertightness of the member is thus obtained at such places andfurther, in cooperation with the stretcher spool 16, they willcontribute to damp the traction pulls during the use of the arrangementin the water. The cylinder 10 is pressed between the plates 13 and 23and consequently does not make contact with the flanges of the spool 16;consequently further, the incident pressure waves on the upper and lowerfaces of the member are not transmitted by said flanges to the cylinder10. When required, further, circular ribs, 14 and 24 are provided in theplates 13 and 23 for better defining in the arrangement the position ofthe piezo-electric cylinder 10 though said ribs do not come into contactwith the upper and lower ends of said cylinder. A flexible cylindricalsheath 12 provided with annular flanges 27 encase the cylinder 10, beingapplied over its external face and the flanges 27 apply over outerportions of the plates 13 and 23, thus maintaining the sheath in itsposition over the cylinder 10 and ensuring watertightness of thecylinder inner volume at such places. Said sheath may be made of rubberor similar plastic material. Being tightly applied to the outer wall ofthe piezo-electric cylinder 10, all pressure elastic waves aretranslated without appreciable weakening to said cylinder.

As a modification shown in FIG. 3, the sheathing of the outer wall ofthe cylinder 10 is made from extensions of the end plates between whichthe cylinder is maintained. The lower plate 33, also provided with itscable sleeve 35, extends in a tubular wall portion 32 ending in anannular flange 34. The upper plate 43, provided with its cable sleeve45, extends in another tubular wall 42 ending in an annular flange 44.The relative dimensioning is such that on the first part, the tubularwall 42 tightly applies over the outer lateral wall of 10 and the flange44 applies under the end annular face of said cylinder 10. Once thestretcher 16 introduced within the cylinder and the connections madebetween said cylinder and the cable, the other sheath 32 of end plate 33is then passed over the sheath 42 so that said sheaths are in tightapplication one over the other and over the lateral wall of the cylinder10. The laterally incident pressure waves will not be appreciablyattenuated as in the arrangement of FIG. 2. The ribs such as 14 and 24may be dispensed with, due to the positioning of the cylinderautomatically obtained from flange 44 and end plate 43.

3 What is claimed is'. 1. A piezoelectric hydrophone for anti-echosubmarine listening comprising incornbination:

(a) a hollow cylinder of piezoelectricmaterialhaving- I inner and outerelectrodes thereon; :-(;b) a rigid hollow spool-shaped member positionedcoaxially within said cylinder and spaced: radially.

inwardly thereoflthe flanges of said spool lying in substantially thesame planes as the end faces of I said cylinder, said spool furtherincluding. a. central.

transverse bore therethrough;

: (.c) a pair ofsubstantially disk-shaped apertnredelastomeric membersoverlying opposite ends of saidspool I i I 2. A hydrophone as defined byclaim '1 in which said disk-shaped members each-include an annular ribon the I facing surfaces thereof, the outer diameter of said rib beingless :than the internal diameter of said cylinder and the inner diameterof said' rib'being greater than the external. I

diameter of the flanges of said spool shaped member. I 3. A hydrophoneas defined by claim 1 in which said spool shapedmernber :is'forrned :intwo-parts which pinchsaid cable therebetween.

' References Cited by-the Examiner UNITED STATES PATENTS 2,762,0329/1956. Vogel 340-10 2,947,969 8/1960 Harris 340-l0. 3,068,446 12/1962Ehrlich 340-10 CHESTER L. J USTUS, Primary Examiner. I

-G. M. FISHER, Assistant Examiner.

1. A PIEZOELECTRIC HYDROPHONE FOR ANTI-ECHO SUBMARINE LISTENINGCOMPRISING IN COMBINATION: (A) A HOLLOW CYLINDER OF PIEZOELECTRICMATERIAL HAVING INNER AND OUTER ELECTRODES THEREON; (B) A RIGID HOLLOWSPOOL-SHAPED MEMBER POSITIONED COAXIALLY WITHIN SAID CYLINDER AND SPACEDRADIALLY INWARDLY THEREOF, THE FLANGES OF SAID SPOOL LYING INSUBSTANTIALLY THE SAME PLANES AS THE END FACES OF SAID CYLINDER, SAIDSPOOL FURTHER INCLUDING A CENTRAL TRANSVERSE BORE THERETHROUGH; (C) APAIR OF SUBSTANTIALLY DISK-SHAPED APERTURED ELASTOMERIC MEMBERSOVERLYING OPPOSITE ENDS OF SAID SPOOL AND SAID CYLINDER, AND INCLUDINGOUTWARDLY AXIALLYEXTENDING TUBULAR PORTIONS CONCENTRIC WITH SAIDAPERTURES AND CYLINDRICAL PORTIONS ENCLOSING SAID CYLINDER INWATER-TIGHT RELATION AND TERMINATING IN RADIALLY INWARDLY EXTENDINGFLANGES; (D) AND AN ELECTRICAL CABLE EXTENDING THROUGH SAID DISKSHAPEDMEMBERS AND SAID SPOOL AND CONNECTED TO SAID ELECTRODES THROUGH SAIDTRANSVERSE BORE.